This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 19 |
| 5 | 155 |
| 6 | 1641 |
| 7 | 21427 |
| 8 | 334377 |
| 9 | 6085683 |
| 10 | 126745435 |
| 11 | 2975448641 |
| 12 | 77779634571 |
| 13 | 2241339267037 |
| 14 | 70604384569005 |
| 15 | 2414086713172695 |
| 16 | 89049201691604881 |
| 17 | 3525160713653081279 |
| 18 | 149075374211881719939 |
| 19 | 6707440248292609651513 |
| 20 | 319946143503599791200675 |